Excessively costly. Maybe some form of detection that can signal to coming trains. But... Dare I say... The clumsy and the suicidal will just take their tragedy elsewhere.

The other advantages of platform doors include:
1) Keeping paper/metal trash off the tracks (more reliable switches & electrical)
2) Being able to fully or partly air-condition stations (or at least keep exhaust heat from trains out)
3) Better loading & unloading (you know where to wait, and there are no accidental steps-into-gap-between-cars)

If you dig back in the Driven By Customer Service thread, there's probably pages worth of Platform Screen Door discussion. We discuss it about once a year on here. I think there might actually have been a thread made at one point...

No mention of this yet, but the MBTA's requirements say the new trains must be designed and proven for 70 MPH and will be expected to run 63 MPH in operation. This is huge since current limits are 50 MPH for Red Line and 40 MPH for Orange Line.

Excessively costly. Maybe some form of detection that can signal to coming trains..

Shep -- that would be quite easy

Set-up one of the mm band radars used on some of the high-end luxury sedans for anti-collision to run along the platform length.

This kind of radar beam is quite narrow over the length of a platform. Locate the beam such that a person falling or being pushed would break the beam on the way down -- but hard for someone messing around on the platform to intentionally trigger the alarm

Provide "an Instant Replay" --- Locate a camera to monitor the same field. Then provide auto detection with auto alarm in the Control Center where the instant replay is constantly storing the last 1 minute of video,

The controller will be responsible for manually triggering the alarm [after mandatory review] -- alarm sent to the Train or Trains approaching the platform -- one station away and the Station itself and 911

If the falling person triggers the auto detection and the nearest train is close -- auto alarm, in the Cab and Station as well at at the Control Center

This can be done for a insignificant cost compared to installing doors on varied platform styles of varying ages and designs

Keep in mind that they already do a lot of monitoring. If you haven't visited the control center at High Street, you ought to go for a tour. It's free.

Math -- I've been there

My point is that you don't want someone to be devoted to monitoring dozens of platforms --- really boring duty --- high probability of error by ommision

Nor do you want to depend on visual analytics for something like a person falling into the "Pit"

The Radar triggers a highlighted video view [highlights courtesy of the video analytics]

The video can be reviewed in a few seconds by the Control Operator who then makes the decision as to how to most appropriately to respond depending on the circumstances [using a prioritized set of guidelines]

Unless the train is imminent to the station [depends on the particular Station]:
spacing of local stations; grade approaching; speed of the tranin; indoor, outdoor; time of day; track conditions; etc -- all part of the CONOPS -- in which case the full auto mode takes over and notifies the Cab and the Station and also 911

No mention of this yet, but the MBTA's requirements say the new trains must be designed and proven for 70 MPH and will be expected to run 63 MPH in operation. This is huge since current limits are 50 MPH for Red Line and 40 MPH for Orange Line.

Don't get too excited. The existing 1969 built #1 Red Line cars were speced and built to be capable of 70 MPH operation too. So far, they have been waiting 44 years to put that capability to use. It is good that they are at least going to continue to maintain the possibility of higher speed operations someday.

definitely could only be fully utilized on Braintree. Can't get up to those speeds many other places on the Red Line.

Braintree's seen gradual decay in speeds as state-of-repair has degraded. Temp speed restrictions becoming de facto permanent. That can be improved right away if they put some elbow grease into the physical plant. The branch has never gotten a substantial wholesale rehab since the Quincy Ctr. extension opened 45 years ago. We're coming up on the half-century mark that's end-of-life for most of the remaining original infrastructure. It's time to start programming funding for rolling railbed/culvert, bridge, cable, power source renewal and quit slacking off on the shorter-lifespan stuff like rail, tie, switch renewal that are most responsible for the gradual creep in speed restrictions.

Downtown it's the mangled signal installation that forces the choke point between Central and SS. The Central-Kendall stretch used to do 55-60 MPH on the old pre-1988 signal system. It's permanently capped at 49 MPH today, and then you have the much slower and dead stop-prone slog at anything resembling peak load because the signal blocks were spaced too far apart for the density. It makes little difference if you kick on the afterburners today, because unless it's in the way off-peak all that means is the train catches up too quickly to one of the crippled signal blocks occupied by a slow downtown train and has to pause for a schedule adjustment. If that happens for 1/3 of the service day already, all raw speed does is ensure it happens 40-50% of the service day and makes OTP even worse.

Keeping the design speed at 70 is something they could tap with CBTC signaling. That solves for the downtown logjam with at minimum tighter-packed blocks restoring capacity to what it used to be, and at best full moving blocks where live train spacing sets the headways instead of rigid blocks. That could bring the Central-Kendall stretch back up to what it used to be without the trains needing to artificially hold back. These vehicles are designed to last 25 years not including rebuilds, so they will see service on some permutation of a next-gen signal system if for no other reason than the current system will hit end-of-life and be up for necessary replacement while these vehicles are running.

Something I noticed in an article about MTA's Sandy recovery in the NY Times is that the L train uses CBTC and therefore wasn't affected as badly by damaged signalling equipment. Putting aside the topic of storm damage, the L could be a model for the Red Line, perhaps?

Something I noticed in an article about MTA's Sandy recovery in the NY Times is that the L train uses CBTC and therefore wasn't affected as badly by damaged signalling equipment. Putting aside the topic of storm damage, the L could be a model for the Red Line, perhaps?

Yes. CBTC substantially reduces the trackside hardware required for signaling and does higher-bandwidth 2-way communication with its lesser hardware requirements, so it requires a lot less maintenance. Very expensive up-front to install, less expensive to operate and maintain once it is installed. The T is studying doing Blue first even though that's the line with the least need for headways because that's the only heavy rail line still using old-timey mechanical trip arms. There are hundreds and hundreds of trackside switches that go up and down and physically strike a target switch on the train to enforce a stop. Every single one of them on the surface portion of Blue has to have a dedicated electric heater so they don't freeze in winter, and the maint staff has to inspect them virtually every night because mechanical things that physically strike the underside of the train wear out quickly and break off all the time in the middle of the service day. ALL of that, plus like four-fifths of the signal lights can get retired in favor of widely-spaced solid-state transmitters and software. It'll pay back its investment over the next 30 years.

This is why the MTA, which uses nothing but those Blue Line-style trip arms and wayside signals on the NYC Subway, is setting aside billions and billions to start replacing everything with CBTC on an enormous scale of neverending construction over the next 20+ years because so much of their hardware is at or beyond end-of-life and going solid-state saves so much down the line. Their trials with it on the little shuttle lines proved successful enough that they're ready to start pushing it out to the mainlines, have all new cars on-order equipped, and retrofit all existing cars that aren't slated for soonish retirement.

It is most definitely what the T is going to employ throughout the heavy rail system. Increased headways are only one of the advantages, and it's entirely up to them whether they want to push that envelope or stay closer to status quo. But enough of Blue/Orange/Red is at end of infrastructure life that the maint simplifying and better resiliency is almost as big a driver. We need service that's on-time, doesn't break down, and isn't decaying from wretched state-of-repair more than we need headways right this second. The new signal tech serves that need and is less a PITA to keep working once it's up and working.